Most Effective Scene *Spoilers*
I haven't watched the whole film yet, but it's online and I started watching it. But the scene that really got to me was when Elliot gets his sense of sound taken, with the two little spikes that go into his ears. Right when they do that, they use this sound effect, a very, very high-pitched, but not overly loud sound that literally hurt my right ear when I heard it, and made me very uncomfortable, because it puts you in his shoes at that one moment and that so far was the best scene. That and the last thing he hears is an audio of his wife saying she loves him.
"IMDB: Where Intelligent Film Discussion Goes To Die" - Scott 'The Foywonder' Foy; Dreadcentral.com